The Patent Citations 1 to 4 which have been proposed by the present applicant disclose an air-driven rotary cutting tool for medical use, dental use or other cutting procedures. The air-driven rotary cutting tool disclosed in these citations has a double-wheel rotor as a means for effectively converting the energy of a pressurized air to a rotating force. The double-wheel rotor has a ring-like hub, a first turbine blade part and a second turbine blade portion formed at the outer circumference of the hub. The first turbine blade portion has a plurality of first turbine vanes and the second turbine blade portion has a plurality of second turbine vanes, the vanes extending radially from the center of the hub.
The air-driven rotary cutting tool disclosed in the Patent Citations 1 to 4 has a grip part to be held by an operator and a head part provided at the tip end of the grip part, and it is formed like a handpiece. The head is formed with a hollow portion, a tubular inner housing which has an outer shape corresponding to the inner shape of the hollow portion is contained in the hollow portion, and the rotor and a bearing mechanism for rotatably supporting the rotor are contained in the inner housing. The rotor is designed so as to be detachable to each cutting tool along the axial center. The head part and the inner housing are provided with an air supply passage for emitting a pressurized air into the first turbine blade portion of the rotor and an exhaust passage for discharging the air supplied from the second turbine blade portion. The inner housing is provided with a connecting channel (guide part) for guiding the pressurized air from the first turbine blade portion to the second turbine blade portion. The pressurized air emitted from the air supply passage impinges the first turbine vane of the first turbine blade portion to rotate the rotor around the rotary axis. Then, the pressurized air is sent to the second turbine blade portion from the connecting passage and impinges the second turbine vane to further promote rotation of the rotor around the rotary axis. Thereafter, the pressurized air is discharged through the exhaust passage.
Thus according to the handpiece with the double-wheel rotor allows the energy of the pressurized air to be used most effectively at two turbine blade portions, thereby resulting in that the cutting tool can be rotated with a high torque feature under a high rotational speed comparing to the conventional handpiece.